The present disclosure relates to a power amplifier module.
A mobile communication device such as a cellular phone includes a power amplifier module that is used to amplify the power of a radio frequency (RF) signal to be transmitted to a base station. For example, in GSM (registered trademark) (Global System for Mobile Communications), the gain of a power amplifier module is controlled to implement slope control (ramp-up and ramp-down) of a transmission signal from a mobile communication device to a base station.
Japanese Unexamined Patent Application Publication No. 2009-100197 discloses a configuration for supplying a voltage VLDO output from a low dropout (LDO) regulator to a collector terminal of each of three-stage amplifiers in a power amplifier module. In the disclosed configuration, the level of the voltage VLDO is adjusted on the basis of a level control voltage Vramp to control the gain of the power amplifier module.
U.S. Pat. No. 7,605,651 discloses a configuration of a power amplifier module that includes three-stage amplifiers, in which a voltage VREG output from an LDO regulator is supplied to the first- and second-stage amplifiers and a constant power supply voltage is supplied to the three-stage amplifier.
As described above, in the configurations disclosed in Japanese Unexamined Patent Application Publication No. 2009-100197 and U.S. Pat. No. 7,605,651, an LDO regulator is used to control the gain of a power amplifier module. In general, an LDO regulator leads to a large circuit size because of large current flow.